Time to monitor diseases in Cerrado wheat crops

Wheat sowing is practically closed in the states of MG, GO, DF, MS and BA. The expectation is for a small reduction in the cultivated area compared to last year, reaching close to 200 thousand hectares. In most areas, it is time to manage diseases by monitoring crops and monitoring climate forecasts.

Rainfed wheat was sown in March and April, and many crops are in the grain filling phase. Attention now is to control of ear diseases. In irrigated wheat, sowing work started later and should end by the beginning of June. Care is taken with the health of the leaves.

According to researcher Vanoli Fronza, from Embrapa's Advanced Tropical Wheat Center, in Uberaba, MG, despite the high incidence of blast last year, the supply of seeds for the 2020 harvest was not affected in a way that would compromise this harvest. year. In rainfed wheat, there was a tendency to reduce area in GO and DF, due to losses from blast in the previous harvest, and, in MG, there were producers who opted for corn or sorghum, with rising prices, to the detriment of wheat. In irrigated cultivation, the increase in the price of beans took space from wheat in some pivots. According to the report from the Minas Gerais Department of Agriculture (may/2020) the reduction in wheat area in the state could reach 14%. Initial estimates point to an area between 170 and 200 thousand hectares in the states of MG, GO, DF, MS and BA.

Disease Management

The incidence of blast during the initial phase of wheat development marked the 2019 harvest in the Cerrado. The occurrence of rain during the dry period, minimum temperatures above 15ºC, duration of plant wetness above 10 hours, cloudy days and high relative humidity created ideal conditions for the proliferation of the disease. The use of more susceptible cultivars and the difficulty in controlling diseases in crops also increased damage to wheat, both in rainfed and irrigated crops.

In this harvest, so far, dry wheat crops have shown good development. In Goiás and the Federal District, rainfed crops already show some symptoms of ear blast, but they do not yet represent losses in wheat. “The good development of the plants so far and the low incidence of blast is leading rainfed crops to a high productivity potential that can reach up to 80 bags per hectare”, assesses Júlio Albrecht, researcher at Embrapa Cerrados.

According to Jorge Chagas, researcher at Embrapa Trigo, in the irrigated system, the recommendation is to always avoid sowing in April, giving preference to sowing in May, reducing the favorable conditions for blast during heading and high temperatures at the beginning of the season. cycle, increasing the productive potential of the crop. “Until the end of grain maturation, producers must monitor their crops daily to use fungicides indicated to control the disease at the correct time”, warns the researcher, remembering that, despite the rain, the forecast of minimum temperatures below 15ºC in The next few days should not favor the incidence of blast: “The solution is to monitor farming and climate forecasts”.

For researcher João Leodato Maciel, from Embrapa Trigo, blast control must be preventive. According to him, in years with climatic conditions favorable to the proliferation of blast, the first application of the fungicide should occur right at the beginning of heading and, the following, every 12 days. The researcher warns, however, that if there are no favorable conditions for infection, it is not necessary to apply the fungicide: “In the conditions of the Cerrado, it is normally the rain that forms the wetness necessary to initiate the infection”. Field experiments determined that commercial fungicides with mancozeb in their formulation were the most efficient in controlling wheat blast. Furthermore, when applying fungicides, it is very important that the volume of spray applied is 200 to 250 liters per hectare. 

In years of high incidence of the disease, irrigation management must be changed. Embrapa's recommendation is to carry out irrigation only during the night. The interval between irrigations should be longer to reduce the time it takes for the plant's surface area to wet.

Other diseases for which producers should be alert are leaf spots, such as yellow leaf spot and brown spot. In this case, the fungicides indicated for control are highly effective, as long as they are applied at the beginning of the appearance of foliar symptoms. “From now on, attention is needed when it comes to disease control, always seeking guidance along with technical information, as the risk of blast, despite being low at the moment, still cannot be ignored completely. Control must be carried out with blast disease in mind, but the blast strategy can also be applied to leaf diseases”, explains researcher Joaquim Soares Sobrinho, from Embrapa Trigo. 

Climate

According to agrometeorologist Gilberto Cunha, from Embrapa Trigo, autumn marks the beginning of the dry season in the Central-West region and in a large part of the Cerrado biome. “In the May-June-July quarter, it is normal to have a period of low rainfall in the Brazilian cerrado. However, there is variability in the occurrence of rain between places in this vast region, with some places where the last rains are a little later in the season and others where the dry period starts earlier”. This particularity, assesses the researcher, can intensify the problems caused by blast in places that record rain in a season that would otherwise be dry, or can cause water deficiency in those where the rains stop earlier, both of which can affect rainfed wheat in the cerrado.

Regarding irrigated wheat, “sowing is still underway or the crops are in the initial phase of the cycle, requiring attention in water management and other cultural treatments to explore the yield potential of this cereal which, in the irrigated system, is quite high ”, points out Gilberto Cunha.

To help producers monitor crops, Embrapa Trigo has been working on applications that analyze climate data to assess the risks of epidemics in crops. 

In the 2019 harvest, the favorable climate condition for the occurrence of blast in Central Brazil was identified in the application SISALERT, developed by Embrapa Trigo in partnership with the University of Passo Fundo. Based on meteorological information, a simulation model assesses the risk of wheat blast occurrence and sends an alert message to registered users.

Another tool is Pic-a-Wheat-Field (“photograph a wheat field”, in free translation). The system was developed by Embrapa and had the collaboration of the University of Kansas aiming at interaction with the producer and technical assistance in supplying the system's database. The user simply needs to turn on their cell phone's GPS and photograph the crop or ears with blast symptoms. The geographic coordinates (latitude and longitude) will be extracted from the photos and identified on the map showing the exact location of the occurrence, which is shared among users. The application is free and available for download on smartphone (iOS or Android system) with a simple user registration. 

Actions to attract new producers

“We observed that wheat is still a somewhat unknown crop for producers in the Cerrado”, says Osvaldo Vieira, general manager of Embrapa Trigo. According to him, a proposal is being finalized, to be presented to the Minister of Agriculture, Tereza Cristina, in the format of an alliance between industry, the productive sector, leaders, research, technical assistance and rural extension to expand technology transfer actions and share knowledge with the Cerrado wheat producer. The work plan should be developed from July 2020 until the end of 2021, with the objective of increasing national wheat production and reducing foreign exchange evasion with imports of this cereal that could reach 10 billion reais this year.

For the leader, the advancement of cultivation in the Cerrado could change the geopolitics of wheat in Brazil. “Today, if we resolve the blast limitation, the Cerrado could reach one million hectares quickly”, analyzes Osvaldo Vieira, and adds: “We have made significant progress in research, with more tolerant cultivars, evaluation of fungicides and more efficient management strategies, more We have not yet reached ideal genetic resistance. Once this barrier is overcome, the Cerrado is a great opportunity for Brazilian wheat, favored by the climate, logistics and liquidity”, highlights Vieira.